Thanks to Felix in Raglan of bsidebeats.com I have been introduced to the stylophone. A remarkable device that has been around for years and a wee search will bring up Rolf Harris and David Bowie as famous people enamoured of its delights.
I found a schematic and I’m going to build one.
T1 is a BJT which is a unijunction transistor and they are available from jaycar. The two outputs from the top of what looks like a diode are B1 and B2 and from the bottom is E1 and apart from that seemingly obscure device all the rest of it is straight forward stuff. Bjt’s have long been used as oscillators… something relaxation oscillators I think… from memory, and circuits with them used as such are in a few of my old beginning in electronics books.
Basically the resistance is in parallel with a capacitance across B1 and E1 and then the output off B2 which feeds a normal oscillator of the type we know as a tremolo… oops, got it wrong.
Okay, the audio oscillator, with output at E1, is across B1 and E1 and this is modulated with the LFO at B2. D1 and D2 are signal diodes or germaniums though either should work and the amp is T3 and would be a low gain device with a high mA rated, up to a watt maybe so a little bigger than a straight signal amp but still a tiny little thing. T2, the LFO amp would be a typical voltage amp transistor like a BC549.
So while I was shown it yesterday I immediately thought it would make an interesting configuration for a beatbox and sure enough… there is a stylophone beatbox.
This article is selling for the low price of US$21.50 and would be a bargain in any neck of the woods especially with all the luck I’ve had building drum machines… which ain’t much!
Funny how the idea I had yesterday about a drum machine version of the stylophone was based on having a round copper board and then having the stylus revolving around the circle at the speed of the drumbeat one wanted… and here it is round!
The required patchbay to change the sequences isn’t there though. Maybe I’ll suggest it to the manufacturers if I can find them.